A fourth Somali national is being treated in an isolation unit in the Transkei after falling ill with an unidentified disease, the Eastern Cape health department said on Friday.

The man, who apparently arrived in South Africa recently, was admitted to the Taylor Bequest Hospital in Matatiele on Thursday, spokesman Sizwe Kupelo said.

Earlier in the week three Somalis were admitted to Mount Ayliff Hospital, and another was declared dead on arrival there.

Kupelo said those four arrived in the Transkei town of Ntabankulu on Sunday and Tuesday.

They had diarrhoea accompanied by dehydration, severe headaches and vomiting.

As a precaution, the three survivors had been put into isolation. Their condition on Friday was stable.

Doctors suspected that the illness could be meningitis, Kupelo said.

Also as a precaution, the department would track down people they had been in contact with in Ntabankulu to guard against any possible spread of infection.